Various processes for bonding thermoplastic films to non-woven webs or other thermoplastic films are known. The present invention is an improvement over the current state of the art non-woven laminate films. The assignee herein, Tredegar Industries is a leader in developing both non-woven/film laminated composites and formed three-dimensional film technology. For example, the Raley U.S. Pat. No. 4,317,792 relates to a formed three-dimensional film and the method for making such a film. In addition, the Merz U.S. Pat. No. 4,995,930 relates to a method for laminating a non-woven material to a non-elastic film.
Various types of formed elastic films and processes for making these films are known. The Wu U.S. Pat. No. 5,422,172 proposed an elastic laminate formed by incremental stretching of the web. However, the resulting the film has a 10% permanent set after 50% elongation which is considered to be a low performance elastic material. Further, the vapor or air permeability of the product is achieved by providing mechanical microvoids.
The Swenson et al. U.S. Pat. Nos. 5,462,708; 5,422,178; and 5,376,430 discloses elastic film laminates having an elastic core layer and at least one polymeric skin layer. However, these films are non-breathable films. There is no suggestion of utilizing a non-woven material as a skin contact layer. Further, the processes of the Swenson et al. patents would require additional materials and processing steps in order to utilize a breathable non-woven material.
The Hodgson et al. U.S. Pat. No. 5, 034,078 discloses a method for forming a heat shrinkable film that exhibits elastic properties only after being shrunk. The product produced by the '078 patent is not breathable and does not utilize a non-woven composite material.
The Knight U.S. Pat. No. 5,336,554 discloses a porous elastomeric film wherein air permeability is provided by the use of laser perforation. The '554 patent proposed a high cost manufacturing process in order to achieve breathability for elastic films and laminates.
The Mitchell et al. U.S. Pat. Nos. 5,068,138 and 4,970,259 disclose the use of blown film to produce a of non-breathable elastomeric films. The '138 and the '259 patents do not address, handle or process the inherently tacky elastomeric film. Further neither patent suggested laminating the elastomeric film to a non-woven material.
There is considerable difficulty in working with and processing elastomeric films to form useful products. The inherent tacky and stretchy characteristics of elastomeric films make the films extremely difficult to process. It is especially difficult to use any elastomeric film as a layer in a multilayer laminate.
The present invention addresses those concerns discussed above. The inherently tacky nature of elastomeric film compositions makes the films difficult to use. For example, in hygiene products, only a small piece of the stretchy material might be used. The steps of removing the film from a roll or festoon, cutting the film to size, and moving the cut film are all hindered by the films' tendency to stick to the processing equipment. The prior art required the use of non-tacky thermoplastic skin layers in order to handle the elastic film in further processing steps.
Further, as products with greater elasticity are used in medical and hygiene applications, skin care issues increase. The more stretchable elastic products conform better to the body so breathability from around any loose fitting perimeter of the product is greatly reduced. The closer fit of the elastic product decreases the air flow to the skin, thus increasing the tendency for the skin to remain undesirably moist.
There is still a continuing need for improved elastic film laminates. It is desirable to provide an elastic film laminate which can be readily incorporated into a finished product without the use of adhesive materials or other additional processing steps. It is also desirable to further improve the elastic films by making the elastomeric films breathable or vapor permeable. The elastic breathable laminate films are useful in disposable products and the like where skin irritation is a concern.
The present invention overcomes the drawbacks described above and provides a breathable and elastomeric laminate comprising an elastomeric film laminated to a non-woven material. The breathable elastomeric laminate of the present invention is formed in a single processing step without the need for additional adhesive materials.